Drafting instrument



Feb. 4, 1969 J, M. COOPER .DRAFTING INSTRUMENT Filed Nov. 22, 1967 J06 M. 442M4 A/fomggs United States Patent Office 3,425,128 Patented Feb. 4, 1969 3,425,123 DRAFTING INSTRUMENT John M. Cooper, P.0. Box 101, Birmingham, Ala. 35202 Filed Nov. 22, 1967, Ser. No. 685,117 US. Cl. 33-107 1 Claim Int. Cl. B431 7/00 ABSTRACT OF THE DISCLOSURE An elongated drafting instrument having an edge thereon for drawing a line and an under side which is movable over a surface on which the line is to be drawn. Pressure applying means is carried by the elongated instrument forcing the portion thereof intermediate its ends upwardly in spaced relation to the surface on which a line is to be drawn.

Background of the invention This invention relates to a drafting instrument and more particularly to an elongated drafting instrument having an edge thereon for drawing a line and an under surface which is movable over a surface on which the line is to be drawn, such as a drafting straight edge, parallel bars or rulers, T-squares and the like.

Heretofore in the art to which my invention relates, difiiculties have been encountered in maintaining drawings in a clean condition as the lines are drawn thereon due to the fact that the straight edges for drawing the lines lie flush with the surface on which the line is drawn whereby the instrument slides from one position to another across the surface of the drawing, thus rubbing and smearing the pencilled lines. Also, with straight edges heretofore employed, wet ink is smeared as the straight edge moves across the inked lines.

Brief summary of invention In accordance with my invention, I provide a drafting straight edge in which pressure is applied thereto so as to force the portion thereof intermediate its ends upwardly in spaced relation to the surface on which the line is to be drawn. That is, the under surface of the straight edge is bowed upwardly and supported by the ends thereof whereby the intermediate portion is retained in spaced relation to the surface on which the line is to be drawn. Accordingly, I eliminate entirely the necessity of providing spacer elements or the like adjacent the ends of the straight edge to support the intermediate portion above the surface of the drawing. Also, a conventional type straight edge tends to sag in the middle when additional supports are added at the ends. My improved structure maintains the central portion of the instrument in spaced relation to the surface on which a line is to be drawn regardless of whether or not the ends of the instrument are supported by auxiliary means.

Drafting instruments embodying features of my invention are illustrated in the accompanying drawing, forming a part of this application, in which:

FIG. 1 is a top plan view showing one form of my invention;

FIG. 2 is a side elevational view of the drafting instrument shown in FIG. 1;

FIG. 3 is an enlarged, sectional view taken generally along the line 3-3 of FIG. 2;

FIG. 4 is a top plan view of a modified form of my invention;

FIG. 5 is a side elevational view of the drafting instrument shown in FIG. 4;

FIG. 6 is an enlarged, sectional view taken generally along the line 6-6 of FIG. 5;

FIG. 7 is an exploded view showing a still further modified form of my invention;

FIG. 8 is a side elevational view of the drafting instru ment shown in FIG. 7 and showing the instrument assembled; and,

FIG. 9 is an enlarged, sectional view taken along the line 99 of FIG. 8.

Referring now to the drawing for a better understanding of my invention, I show in FIGS. 1 through 3 a drafting instrument embodying an elongated member 10 having an under surface 11 which is adapted to move over a surface 12 on which a line is to be drawn. The elongated member 10 is provided with parallel straight edges 13 and 14 for drawing a line on the surface 12 in a mar.- ner well understood in the art to which my invention relates. The elongated member 10 is formed of a bendable, resilient material, such as plastic, metal and the like.

Secured to the top of the elongated member 10 and extending substantially the length thereof, as shown in FIGS. 1 and 2 is an elongated housing 16 having a downwardly opening, longitudinally extending recess 17 which extends the length of the housing. The ends of the housing -16 are closed by vertically extending end walls 18 and 19. The housing 16 is secured to the elongated member 10 by suitable means, such as retaining screws 21 which are in threaded engagement with the legs of the housing 16 and fit within countersunk recesses in the elongated member 10 whereby the heads of the screws 21 are flush with the under surface of the elongated member 10.

Extending longitudinally of the downwardly opening recess -17 is an elongated tension member 22 which may be in the form of a steel bar, wire or the like. Openings are provided in the vertical end walls 18 and 19 for receiving the ends of the elongated tension member 22 whereby the ends of the tension member are supported in spaced relation to the upper surface of the elongated member 10. One end of the elongated tension member 22 is provided with a head 23 which is adapted to engage the outer surface of the vertical wall 18. The other end of the elongated tension member 22 is threaded as at 24 for receiving a nut 26 or other suitable tightening device whereby the effective length of the tension member 22 may be varied by tightening or loosening the nut 26.

Extending transversely of the housing 17 intermediate the ends of the tension member 22 and the housing 17 is a tension applying member 27 which may be in the form of a transverse pin-like member. The tension applying member 27 engages an intermediate portion of the elongated tension member 22 at a point which is closer to the elongated member 10 than the end portions of the tension member 22. That is, the tension applying member 27 extends above and engages tension member 22 whereby upon tightening the nut 26, the tension member 22 tends to straighten out and thus applies pressure to the transverse member 27 which in turn forces the intermediate portion of the housing 16 and the elongated member 10 secured thereto upwardly into an arch with the under side 11 of the elongated member 10 bowed upwardly and supported by the ends of the elongated member 10 in spaced relation to the surface 12 on which a line is to be drawn, as clearly shown in FIG. 3.

In FIGS. 4, 5 and 6 of the drawing, I show another form of my invention in which an elongated tension member 22a extends along the upper surface of an elongated member 10a having an under side 11a disposed above a surface 12 on which a line is to be drawn. The tension member 22a is preferably in the form of a relatively flat strip of material and is secured to the elongated member 10a by suitable retaining screws 21a.

The tension member 22a is secured to the elongated membera while the elongated member llla is expanded or extended relative toits normal length. This may be accomplished by heating or mechanically extending the elongated member 10a beyond its normal length whereby upon releasing the forces which extend the elongated member 10 or upon return of the elongated member 10 to its normal temperature, the overall length thereof is reduced. Also, at the time the tension member 22 1 is secured to the elongated member 10a, the tension member 22a is contracted relative to its normal length. This may be accomplished by reducing the temperature of the tension member 22a to a temperature below its normal temperature or by applying compressiveforces t0. the tension member 22a. After the tension member 2211 is secured firmly to the elongated member 10a, the tension member 22a and the elongated member 10a are allowed to return to their normal temperature, or stresses are removed, whereupon the tension member 22a expands and the elongated member 10a contracts to thus force the intermediate portion of the elongated member 10a upwardly into an arch whereby the ends only of the elongated member 10a are in contact with the surface 12 on which a line is to be drawn. The intermediateportion of the elongated number 10a is thus spaced from the surface 12, as clearly shown in FIG. 6.

In FIGS. 7-9 of the drawing I show a further. modified form of my invention inwhich the drafting instrument is in the form of an elongated member 10b having an under surface 11b disposed to move over the surface 12 on which a line is to be drawn. An elongated tension member 22b is secured to the upper surface of the elongated member 10b by suitable retaining screws 21b. The elongated member 10b has a different coefficient of ther mal expansion from that of the tension member 22!). The tension member 22b is secured to the elongated member 1011 at a predetermined temperature which is different from the normal temperature under which the drafting instrument is used so that upon returning the tension member 22b and the elongated member 10b to their normal temperatures the tension member is extended and the elongated member 10b is contracted relative to each other to force the intermediate portion of the elongated member 10b upwardly into an arch shape to position the under surface 11b in spaced relation to the surface 12 on which a line is to be drawn.

From the foregoing, it will be seen that I have devised an improved drafting instrument. By providing a drafting straight edge which includes means for applying pressure in a direction to force the portion of the straight edge intermediate its ends into an arch with the under side thereof bowed upwardly and supported by the ends of the straight edge, the entire straight edge with the exception of the extreme ends thereof is held in spaced relation to the surface on which a line is drawn. By providing a drafting instrument which is bowed upwardly away from the surface on which the line is to be drawn, the drawing may be maintained in a clean condition at all times due to the fact that there is no rubbing contact 'between the instrument and the surface on which the drawing is made. Also, there is no danger of smearing ink drawing with my improved drafting instrument due to the fact that the under surface of the drafting straight edge is held in spaced relation to the surface on which the ink is applied. Furthermore, by forming the drafting instrument of a resilient, bendable material, the drafting straight edge may be forced downwardly into contact with the surface on which a line is to be drawn whereby upon release of downward pressure, the straight edge returns to its bowed position with the portion intermediate its ends in spaced relation to the surface on which a line is to be drawn.

While I have shown my invention in several forms, it will be obvious to those skilled in the art that it is not solimited, but is susceptible of various other changes and modifications without departing from the spirit thereof,

and I desire, therefore, that only such limitations shall be placed thereupon-as are specifically set forth in the appended claims.

What I claim is:

1. In a drafting instrument embodying an elongated member having an under side disposed to engage a surface on which a line is to be drawn and having a straight edge thereon for drawing a line on said surface, the improvement which comprises:

, (a) an elongated tension member extending longitudinally along the upper side of said elongated member,

(b) support members adjacent the ends of said elongated member supporting the ends of said tension member at spaced locations above said elongated member,

(c) a tension applying member intermediate the ends of and operatively connected to said elongated member engaging an intermediate portion of said elongated tension member at at least one pointwhich is closer to said elongated member than said spaced locations of said support members, and

(d) means adjusting the effective length of said elongated tension member so that upon reducing said effective length said elongated'tension member moves said tension applying member upwardly to bow said under side of the elongated member upwardly in spaced relation to the surface on which a line is to be drawn whereby said elongated member is supported by its ends.

References Cited UNITED STATES PATENTS 2/ 1894 Frank 33-407 2/19-18 Waters 33-107 6/1932 Schenkein 33-107 FOREIGN PATENTS 131,898 2/ 1933 Austria.

HARRY N. HAROIAN, Primary Examiner. 

